ENHANCEMENT OF THE MOLECULAR ION YIELD IN PLASMA DESORPTION MASS-SPECTROMETRY USING EXPLOSIVE MATRICES

The working hypothesis of this study was that the chemical energy of m atrix material may be released, although only on a microscale, under M eV ion bombardment and may assist ejection of large intact bioorganic molecules, To test the hypothesis, the performance of several common e xplosives, as matrices in plasma desorption mass spectrometry, was com pared to the standard matrix, nitrocellulose (NC), which is also a hig h explosive. Two explosives, RDX and HMX, were found to be new, effect ive matrices for peptides and proteins, While the performance of RDX w as comparable with that of nitrocellulose, HMX gave a superior molecul ar ion yield and a higher average charge state of desorbed molecular i ons compared with NC, Noth RDX and HMX have a similar chemical composi tion and structure, although the latter is a more powerful explosive, The measured total ion yield allows the conclusion that the increase i n the amount of ejected material, due to the chemical energy release i n high explosives under MeV ion bombardment, is limited, perhaps to a factor of 2 to 3, The fact that not all tested explosives gave molecul ar ions from peptides and proteins suggests that other factors, such a s gas-phase chemistry, may play a significant role in molecular ion fo rmation. (C) 1997 by John Wiley & Sons, Ltd.